Conventional radio architectures employ a radio frequency (RF) front-end receiver and a base-band processor. In general, the front-end receiver receives a RF signal. For instance, the front-end receiver may include an antenna for receiving RF signals. The front-end receiver may further include one or more tuners for tuning to a particular channel (or frequency). The front-end receiver outputs the received signals (e.g., for the channel to which it is tuned), and the base-band processor receives those output signals from the front-end receiver and processes the signals to, for example, perform certain conversions and/or other processing to control the output of information contained in the signals to a human interface, such as processing the signals to produce audio signals for output to audio speakers. In this way, as one example, content (e.g., music and/or other audio content) may be broadcast via AM and/or FM, and a radio may employ a front-end receiver (with an AM and/or FM tuner) for receiving RF signals for a channel to which it is tuned and a base-band processor for processing the received signals to produce audio output of the corresponding content carried on the received RF signals.
A real-time loop is generally implemented between the front-end receiver and base-band processor through which certain handshaking signals are communicated so that the base-band processor knows exactly what the front-end receiver is doing at any time and vice versa. Such communication over the real-time loop has traditionally been critical because, for example, there are certain times when the front-end receiver is not outputting a proper signal. For instance, during the time when the front-end receiver is tuning from one channel to another, the front-end receiver is not outputting a clean payload signal for the desired channel to which it is being tuned (but may instead be outputting noise). The base-band processor is informed of such a condition so that it can properly control its output (e.g., to potentially avoid or minimize the output of static to the speakers).
One example of a conventional radio architecture (e.g., conventional car radio architecture) is shown in FIG. 1. Architecture 100 of FIG. 1 includes a front-end receiver 101 that has an antenna 102 and an AM/FM tuner 103. Architecture 100 further includes a base-band processor 104 that has an intermediate frequency (IF) converter 105, audio digital-to-analog converter (DAC) 104, channel decoder with AM/FM demodulator and phase diversity functions 107, and digital sound processor 108. In this example, architecture 100 further includes a host central processing unit (CPU) 110, which may be a microprocessor, and audio power amplifier(s) (e.g., 4 channel audio PA) 109. Thus, this conventional architecture 100 includes a dedicated processor (104) that performs processing (e.g., AM/FM demodulation) of the payload signal 111 received from front-end receiver 101, and further includes a host CPU 110 that controls processor 104 and/or tuner 103 based on non-payload information (e.g., status information) exchanged in the realtime loop (e.g., via interfaces 112 and 113).
In operation, an RF signal is received by front-end receiver 101, via antenna 102. Tuner 103 outputs an analog or digital IF signal 111 to base-band processor 104. Base-band processor 104 processes the IF signal 111 (e.g., under control of host CPU 110), and the audio DACs 106 output a corresponding analog audio signal 114 to the audio PA 109.
In system 100, the front-end receiver 101 and base-band processor 104 are implemented on separate chips (on separate silicon substrates), and are thus separate integrated circuits (ICs). As mentioned above, handshaking signals are communicated between the front-end receiver 101 and base-band processor 104. In this example, a real-time loop is implemented via handshaking lines 112 for communicating status information from front-end receiver 101 to base-band processor 104, and via the Inter-Integrated Circuit (I2C) interface, Serial Peripheral Interface (SPI), or Two Wire (TW) interface 113 for communicating information from host CPU 110 to front-end receiver 101. Information such as channel is tuned (phase-locked loop (PLL) is locked) is communicated from front-end receiver 101 to base-band processor 104 via lines 112, and information such as an increase/decrease in gain due to IF converter operations is communicated from host CPU 110 to front-end receiver 101 via the I2C interface 113.
The real time loop is needed in this architecture for making inaudible channel changes or channel checks (also called AF update), as examples. Thus, in this conventional architecture 100 the payload (e.g., the analog IF signals for the received RF signals) is communicated from front-end receiver 101 to base-band processor 104 via a first interface 111, and separate interface(s), such as interfaces 112 and 113, are employed for exchanging status information between the front-end receiver 101 and base-band processor 104/host CPU 110. For instance, the status information communicated via the real time loop is communicated separate from the payload.
Again, in this conventional architecture 100, dedicated processor 104 performs the AM/FM demodulation controlled by host CPU 110. Thus, dedicated processor 104 is implemented for processing the payload signal received from front-end receiver 101, while a separate host CPU 110 is implemented for to control base-band processor 104 and front-end receiver 101. Furthermore the CPU can initiate an action, e.g., channel change, via interface 113. The action itself is executed between tuner 103 and base-band processor 104 by use of status information communicated between the front-end receiver 101 and the base-band processor 104 via interface 112.
More recently, software-defined radio systems have been proposed. In general, a software-defined radio system, or SDR, is a radio communication system where components that have conventionally been implemented in hardware (e.g., mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded computing devices. A basic SDR system may include, for example, a personal computer equipped with a sound card, or other analog-to-digital converter (ADC), preceded by some form of RF front-end, such as the front-end receiver 101 of FIG. 1. Significant amounts of signal processing may be handed over to the general-purpose processor, rather than being done in special-purpose hardware, such as the dedicated digital signal processor (DSP) 104 of FIG. 1. SDR architectures may enable a radio which can receive and transmit widely different radio protocols (sometimes referred to as a waveforms) based solely on the software used.